A quick look at available sources doesn't indicate any of that model seat available, except for one I found in biscuit. I'm pretty sure your toilet is white or you would have told us. Want one in biscuit? I can tell you where to get it. Otherwise, doesn't look like they are exactly easy to find.

And they are absurdly-expensive. But so are all the parts for this esoteric item.

The good news is that the mounting holes for the bolts are in the same standard 5.5" centered layout that all but the most exotic of toilets use. There are a lot of opportunities to find a replacement. And with your budget of more than $150 for a Porcher seat, you will have a whole lot of options, provided that they open cleanly in that little restricted area around the toilet tank.

You could get yourself a nice bidet seat, or see if Porcher recommends one of their newer seats for this model. Or, you could make yourself a little template of the space around the bolt holes, and visit a good store to see if they have a seat you like. You might check out the dimensions of some of the Toto seats, like the SS114; perhaps one of those would fit the bill for you. And you'd have over a hundred dollars still in your pocket.

Update: I just looked at the spec sheet for the Toto SS114, which looks somewhat similar to your seat (although it has varied in design in the last few years and all the designs have the same model number; one looks kind of like yours and one doesn't). In any event, the spec sheet says that the Toto is 18.5 inches from the center of the mounting holes to the end of the seat. Your Porcher is 16.25. So you need a shorter seat than the SS114.